Vestibular migraine (VM), defined as vestibular symptoms such as vertigo generated by migraine mechanisms rather than other inner ear or brain abnormalities, is a common and disabling problem. Despite its frequency, the pathophysiology of VM remains uncertain and no specific oculomotor, postural, or perceptual defect has been described in this disorder. This proposal investigates the pathophysiology of VM using quantitative psychophysical and oculomotor tests with the underlying hypothesis that the rotational information provided by the semicircular canals and the gravito-inertial information provided by the otolith organs are synthesized abnormally by the brain in VM. Three inter-related experiments will be performed to investigate this hypothesis. In VM subjects and controls groups (normal subjects, migraine patients without dizziness, dizziness patients without migraine), we will measure the effects of vestibular stimulation on perceptual thresholds (SA1), perceived magnitude of tilt and translation (SA2), and eye movement responses (SA3). Perceptual and eye movement responses are predicted to show evidence of enhanced canal-otolith interactions in the brain such that they are augmented when these two cues are congruent (e.g. roll tilt), are inhibited when the cues conflict (e.g. centrifugation), and are noral when the canals and otoliths are activated in isolation. These predictions are supported by the extensive preliminary data collected to support this proposal. This research will help to elucidate the mechanisms responsible for vestibular symptoms caused by migraine, could be critical for developing diagnostic tests that help to identify VM, and could also provide a scientific rationale for treating patients with this disorder. PUBLIC HEALTH RELEVANCE: This project will investigate patients who have dizziness caused by migraine (vestibular migraine) and control subjects using use perceptual and eye movement testing. The goal is to improve understanding of vestibular migraine by helping to elucidate its underlying pathophysiology.